


Hearts of Blood

by neonbees



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: (attempted), Alternate Universe - Vampire, Blood Drinking, Graphic Description of Bood, It’s consensual mind control, M/M, Mentions of Dimitri & F!Byleth, Mind Control, Unresolved Sexual Tension, Vampire!Sylvain, Vampires, but damn do i love vampire aus, id like to formally apologize for being thirsty on main
Language: English
Status: In-Progress
Published: 2019-08-24
Updated: 2019-08-24
Packaged: 2020-09-24 13:04:42
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,106
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20358970
Author URL: https://archiveofourown.org/users/neonbees/pseuds/neonbees
Summary: Vampire!AU For Three Houses.Sylvain and Felix discuss their new professor, Dimitri, and then sneak into the infirmary for a little bit of practice. In that order.





	Hearts of Blood

**Author's Note:**

> Half of this is AU set up. Skip to the line break if you're just looking for some Vampire Sylvain/Felix.
> 
> I'm not /entirely/ sure what to tag all this with. So uh, warning for some vampire-typical scenarios in this? Aka, blood drinking, injury for the purpose of blood, etc.

“So, what do you think of the new professor?” 

Sylvain’s excuse was that he was here to train, but his own lance was far from his hand. The redhead sat on a bench, chin cupped in his hand as he watched Felix lazily. The sun had just set, the sky bleeding crimson over the horizon. 

“Jeralt’s daughter? She seems to be a worthy training partner. Her skill with a sword is honed by years of mercenary work. An admirable adversary, to be sure.”

“...But?” Sylvain pressed, knowing there was more. Felix, only complimentary? That’d be a sight.

“I admit that I am surprised. Why she was chosen to teach _here_.” The emphasis on the place- Garreg Mach Monastery. An Officer Academy- and a place where the Goddess’ most beloved came to train.  
Byleth hadn’t seemed so blessed- odd, yes. But she wasn’t like Sylvain, or even like Felix, who was closer to the mundane than he was. 

“She doesn’t have a heartbeat, you know.” 

“Neither do you.” 

“_Hey!_ I do have a heartbeat, you know. It’s just slow. Unless I’m with someone cute~” Sylvain waved the thought off with a gesture, “You’re distracting me! I just want to talk about it. She doesn’t have a heartbeat, but her blood is still - I don’t know, flowing, I guess? It’s bizarre.” 

Felix frowned, this time giving Sylvain his full attention. “But she’s not like you.”

“Well, she could be something else- like you know how Dedue is! But no, she’s not like any of us. She smells… I can’t describe it. But you’ve got that sense, don’t you? You should already know what she’s like. When I get too close, it’s almost intoxicating. I bet she tastes-”

“Ugh, shut up. You’re revolting.” Felix scowled, the sharp thwap of his training a sword against a dummy adding more weight to his words. Not that Sylvain ever seemed to care. “... Besides. The boar’s here.” 

“Ahh yeah. You’re next to him, aren’t you? It’s been what, two years?” 

“Two years that I’ve gone without that stench of blood,” Felix hissed, “And now he’s back. Right next door. He’s hiding his bloodlust most days. But when he rests… He hungers, Sylvain. His lust for bloodshed chokes me; I want to retch. It’s the worst when he wakes. When he reaches out, I can feel his rage. Somehow, he’s become more diseased than before. He masquerades around like he’s normal, like he’s not just an animal in the shape of Dimitri- It disgusts me.” 

“...Hey. Did you want to practice again? And he has Dedue, Felix. It doesn’t have to be you.” 

“I’m to be Duke Fraldarius, Sylvain. I’m to be his _regulator_. Dedue is his lapdog- do you think he’d prevent anything ‘His Highness’ wants?” 

The quiet was answer enough. Sylvain knew it was true- much as he wished it wasn’t. Glenn’s death had changed everything for them. 

In the Kingdom and the Empire, a common practiced reigned through both lands. The idea of a regulator- the one to watch over the nobility, to make sure that they did not step out of line. There was even a similar practice in the Alliance, he knew. But the one in the Kingdom was one that revolved around the monarchy. 

Dimitri was a vampire lord- his bloodline gave him abilities that the rest of the vampiric nobility could only dream of. The existence of a Regulator, someone who had a foot on both sides, human and vampire, gave safety and assurance to the common people. The King could not simply ignore his human citizens- the Regulator would not let him. 

This role typically fell to the Duke of the Kingdom- The Fraldarius family had held this position for generations. Rodrigue and Lambert had held a powerful bond, and it was expected that would repeat itself in Glenn and Dimitri, once the two were old enough. 

The Regulator and the King- they would share blood, and with it, the Regulator would be immune to any charms a vampire could possess. The bond was known to become so powerful that feelings could be shared as well- possible, even memories. 

Glenn had been the one two watch over Dimitri. 

And Felix had been the one for Sylvain. 

The Margrave was a militaristic role- and an important one. Safeguarding the border was their role, and they had the command of armies to prove it. There were very, very specific restrictions on who could be the heir. They needed to be Goddess Blessed- in both vampiric hereditary, and with a crest. 

The King, the Regulator, and the Marcher Lord. Sylvain sometimes felt like a piece on a board, born into a role and cast into its shape. But at least, he’d had solace in friendships. Felix, Glenn, and Ingrid were often over, as was Dimitri. Their intertwined future put them together- but they’d made those friendships by choice. Sylvain wanted one thing to call his own. 

Felix would not be his, not completely. He wondered how Ingrid had been alright, knowing she’d had to share Glenn like that. He figured though, that she would have traded anything to have him back again. 

Still, he supposed there was one thing he had. This- 

Dimtri was supposed to be the one to let Felix drink from him, and to take from him in return. Even without any other ritualistic aspects, it was necessary to keep Felix Human, and to keep him resistant. 

But Dimitri hadn’t been able to, those four years ago, and Felix would never let himself be weakened. They’d struck an agreement- Sylvain’s blood could be used to continue to boost Felix’s immunity, and in return, Felix would keep Sylvain satiated. 

\---------------------------------------------------------------------------------------------------------------------

‘Practice’, they called it. 

Really, it was more than that. 

There were many empty rooms within the monastery. Most often, it was the physician’s room they used- Manuela was hardly ever there, and the smell of blood wouldn’t be too noticeable among the other chemical smells. 

Sylvain shut the door behind him, already feeling the eagerness in his own body. His fangs, extending with his own growing desire, the heat in his stomach and the _hunger_ that was ever present for a vampire. Goddess, if they were truly so blessed, why was he always so wanting- 

“Come here,” Felix commanded, sitting on an empty bed, curtains drawn back. “I’ll go first. I do want to practice my resistance. If I let you take what you want, you’ll never be able to control yourself.” 

“I’ve got good self control,” Sylvain wheedled, but did as Felix commanded, moving closer. He always made a token resistance. But he would do whatever the other wanted. They’d only have this for so long. 

He wanted to sit between Felix’s legs, kneeling at his feet as he pressed his lips to his wrist, but that could wait. At least, with Felix going first, they had some excuse for doing this. Or perhaps it was the truth for Felix. Still, Sylvain would take would he would get.

He sat next to Felix, bringing up his wrist to his mouth, biting down sharply. The pain was familiar, and by now, had become something he’d associate with pleasure, if only for what came next. He let the blood run down his hands, dripping down his fingers- but nothing wasted. 

Because Felix was there, taking Sylvain’s fingers into his mouth. Sucking the blood off of them, tongue pressing against the sensitive digits of Sylvain’s fingers. He was always so tempted to press deeper- get his friend to suck him a little bit harder, press against his tongue . Goddess, it was only his fingers and yet, Sylvain could feel heat running through his body. 

A vampire had a slow heartbeat, and yet, he would swear it would speed up with Felix. 

But he was quick healing, and eventually the wound closed. Felix pulled away from Sylvain, just the slightest hint of red to his lips- and Sylvain felt like he was on _fire_.

“Command me,” Felix ordered, eyes half lidded. But even that didn’t disguise the curve of red around his iris, the presence of Sylvain’s blood already taking effect. 

Dimitri’s abilities were in obedience and fear- and Sylvain’s were in charm and destruction. His charm would never be as powerful as anything from Dimitri, but it would still allow Felix to practice. 

“Lay down on the bed,” Sylvain whispered, voice hoarse, and yet, he could feel the undercurrents of power in his words, the Gautier crest activating with its desire to ruin- but Sylvain controlled it. The charm was his personal ability- not his house’s. 

“I refuse,” Felix said, not even a blink, “Give me something harder. I need a challenge.” 

_Kiss me_, Sylvain thought. But he needed something that Felix wouldn’t want to do- the more reasonable an order was, the harder it was to refuse. “Go train,” he murmured, coaxing, forcing more power into his words, “You left your sword at the arena. Go, pick it up, before someone else moves it.” 

He watched carefully as the muscle in Felix’s jaw worked, the other fighting against the command- why didn’t he want to go pick up his own weapon? It was quite reasonable. The thoughts would work against Felix, but Sylvain was confident that the other could overcome it. 

Felix would train and train until he succeeded. 

“I refuse,” Felix ground out, the red in his eyes flickering. “You’re getting better at picking less stupid commands. You make it too easy, Sylvain. I’ll still feed you, but I will train first.” 

“Fine, fine,” he laughed, practiced, easy. Hiding his deeper feelings. “Let’s go a few more times. Don’t you want to do something for me?” 

Felix’s no came almost a minute later, “More clever than I’d expect from you. I hadn’t thought that would be a command.” 

“You need to be more prepared, that took you almost a minute to recover from,” Sylvain shook his head, “Want to do another, or is that enough for tonight?” 

“It’s fine for now,” Felix huffed, shaking his head. And then, his deft fingers got to work, top slipping off as he then moved to unbuttoning his undershirt.

“I’m not that messy,” he rolled his eyes, a token protest against Felix’s actions. He would always remove his shirt, and it always became that much harder for Sylvain to control himself. But that didn’t mean he wanted him to stop. 

And perhaps in response to Sylvain’s own commands, Felix responded with one of his own, “Come on, Sylvain. Are you not hungry?” 

For you, he was. Sylvain moved swiftly, one arm on the other side of Felix, the other cupping his head as he tilted his neck, baring the soft flesh for access. He could feel himself salivating, the heated desire obvious in his eyes. He brushed the tips of his fangs across Felix’s neck, feeling him shiver. “Do it,” Felix ordered.

And so Sylvain bit down, fangs sinking into the other’s neck. The hot taste of Felix’s blood, spiced, almost, but oh so pleasant, filled his mouth. He moaned, uncontrolled, tongue lavishing the wound as he sucked for more. 

He could feel the shudder of Felix’s body under him, a response to the pleasure/pain a vampire could bring. The initial pain of the bite, overwhelmed with pleasure soon after. His saliva worked both to soothe and to close the wound when necessary, his fangs reopening it when the blood flow stopped. 

But he could never take too much- Sylvain stopped drinking, pressing an open kiss to seal the wound closed. And if he kissed Felix’s neck once more, well, he just wanted to make sure his friend healed properly. 

He leaned back, looking at Felix’s roughened state. His neck, bruised, traces of blood that Sylvain desired to clean with his own mouth, and his breathing heavy with emotion. He could imagine it. Kissing down the planes of Felix’s stomach, biting and teasing at those areas he knew were sensitive. Felix would squirm underneath him. And if he could get him to moan- well, now that’d be music. 

“If you are done. I think I’ll sleep here tonight,” Felix murmured, his hand feeling the wound on his neck. “I don’t want to be next to the Boar while he sleeps.” 

A statement. Not an invitation. Sylvain reminded himself. That’s how it was. “Alright, Felix,” he sighed. “Let me bring you something to eat, first. I don’t want you to wake up woozy.”

“Nothing sweet.”

“Don’t you think I know that,” Sylvain rolled his eyes, standing up- reluctantly. “I’ll be back soon.”

He listened to Felix’s heartbeat on the way out.

**Author's Note:**

> one day, i'll write them resolving their sexual tension, i swear.
> 
> definitely doing more of this au. i'd love to write vampire!dimitri/byleth... if i can stop thinking abt sylvain for 5 minutes. send help.


End file.
